Basic aluminum halides, or aluminum halohydrates, are well known antiperspirant compositions. The addition of zirconium compounds to aluminum complexes generally enhances the efficacy of the antiperspirants because of the depolymerization of aluminum species in the presence of zirconium. As the concentration of zirconium increases, more monomeric and low molecular weight aluminum cations are formed, and changes in the structures of the polymers are also observed.
Higher charge/size ratios and faster hydrolysis rates for Zr4+ ion hydrolysis complexes also account for improvements in aluminum-zirconium antiperspirants over the use of antiperspirants containing solely aluminum. However, the presence of zirconium species decreases the stability of the corresponding aluminum-zirconium antiperspirant solutions because zirconium hydrolysis species precipitate at a relative lower pH than the corresponding aluminum species. Glycine is generally added in order to stabilize the aluminum-zirconium antiperspirant solutions. It is believed that the complexation between zirconium and glycine stabilizes the aluminum-zirconium antiperspirant solutions. The presence of too much glycine, however, tends to decrease the antiperspirant efficacy of aluminum-zirconium antiperspirants. Further, the use of amino acids, such as glycine, introduces an additional relative expense to the preparation of the antiperspirant.
Current commercial aluminum-zirconiun-glycine salts (ZAG) and compositions contain glycine, with the Zr:glycine weight ratio being approximately 1:1. US patents disclosing composition of this kind include U.S. Pat. Nos. 4,775,528; 5,114,705; 5,225,187; 5,486,347; 5,589,196; 5,955,064; 6,066,314; EP 0 653 203 A1 with respect to antiperspirant compositions containing polyhydric alcohols.
U.S. Pat. No. 6,074,632 disclose antiperspirant salts in stabilized aqueous polyhydric alcohol solutions. The polyhydric alcohols have from 3–6 carbon atoms and 3–6 hydroxyl groups. The highest concentration of Al—Zr active in the solution has about 36% anhydrous solid.
U.S. Pat. No. 5,939,057 presents a product comprising a clear polyhydric alcohol solution of about 20 to 50% by weight of active, about 2 to 16% by weight water, and a glycine to zirconium ratio of about 1.3:1 to about 4:1. The product of enhanced efficacy aluminum-zirconium chlorohydrate glycinate has an HPLC peak 4 to 3 ratio of at least 0.7. The process of making such product involves making an activated aluminum antiperspirant solution by diluting and heating, followed by addition of zirconium hydroxyl chloride glycinate solution and polyhydric alcohol, and rapidly evaporating the water under vacuum. Such process is lengthy and not economical.
WO 01/56539 A1 involves a process of making Al—Zr active salts in polyhydric alcohol solutions by the direct react of aluminum salt aqueous solution with zirconium oxychloride crystal, a polyhydric alcohol, aluminum metal and optionally an amino acid buffer. The reaction temperature is maintained at about 100° C. to 140° C. to provide an Al—Zr complex in the polyhydric alcohol at a concentration of about 20 to 45% A.S. The amount of polyhydric alcohol is 20 to 70% by weight of the final antiperspirant solution. The product has a HPLC Band III and IV of at least 60%, and Ala is from 25 to 55% by Ferron analysis. The invention involved a direct process. The product does not include an antiperspirant active with lower polyhydric alcohol content of less than 20% by weight.
WO 02/34211 A2 comprise aluminum zirconium salts having a metal to chloride molar ratio in the range of 0.9–1.2:1 and glycine to zirconium molar ratio greater than 1.3:1. It is necessary that glycine be present in order to obtain the desired product.
WO 02/34223 A2 discloses enhanced efficacy aluminum zirconium antiperspirant salt compositions have a metal to chloride ratio of about 0.9 to about 1.0. Such compositions exhibit an HPLC peak 5 area content of about 33% to at least 55%. However, an amino acid has to be present to afford the enhanced efficacy antiperspirant salts.
From the status of the known prior art, it is regarded as desirable to provide a stable aluminum-zirconium antiperspirant having a high active content and easy to make that does not require the inclusion of amino acid, such as glycine.